CFD Approach for Analyzing the Variation of Flow Parameters and Losses in a Mixed Flow Francis Turbine

Abstract

Francis turbine can be used for a wide range of head and discharge, thus it is the most versatile water turbine in use [1]. As load varies from full load; the regime of operation changes for meeting the required power demand on electric system [2]. Efficiency of Francis turbine drops significantly at part load and overloading operations due to increased shock losses at the entry to runner, eddy formation and increased swirl in draft tube and head loss in various parts of the turbine. So, it becomes very important to evaluate the performance of turbine at off design conditions before installing them on site. For performance evaluation, calculation of various flow parameters at inlet and outlet of runner and determination of losses in different parts play the most important role. In the present work, flow simulation in a3 MW capacity horizontal axis mixed flow Francis turbine is done using ANSYS CFX 14.0. The simulation is carried out for four different guide vane openings according to the load onturbine (here 60, 80, 100 and 120% loads are considered) and for each GVO, nine speeds from 450 to 850 rpm are taken. The flow parameters variations from inlet to outlet of the runner and head loss in different parts are calculated at these operating conditions. It is found that at 100% load, losses are minimum. Apart from this, coefficient of pressure is calculated through runner blade passage for analysing the distribution of pressure on runner blade.
Cite this ArticleGyanendra Tiwari, Vishnu Prasad,Shukla SN. CFD Approach forAnalyzing the Variation of FlowParameters and Losses in a Mixed FlowFrancis Turbine. Journal ofExperimental & Applied Mechanics.2016; 7(2): 54–65p.